Academic literature on the topic 'Rhyolite calderas'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the lists of relevant articles, books, theses, conference reports, and other scholarly sources on the topic 'Rhyolite calderas.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Journal articles on the topic "Rhyolite calderas"
1
Coyle, Marylou, and D. F. Strong. "Geology of the Springdale Group: a newly recognized Silurian epicontinental-type caldera in Newfoundland." Canadian Journal of Earth Sciences 24, no. 6 (June 1, 1987): 1135–48. http://dx.doi.org/10.1139/e87-110.
Full textAbstract:
Volcanic–sedimentary facies and structural relationships of the Silurian Springdale Group in west-central Newfoundland are indicative of a large collapse caldera with an area of more than 2000 km2. Basaltic flows, andesite flows and pyroclastic rocks, silicic ash-flow tuffs, high-silica rhyolite domes, and volcanically derived debris flows and breccias, fluviatile red sandstones, and conglomerates make up the group. It is bounded on the east and west by up-faulted basement rocks, which include gneisses, amphibolites, and pillow lavas, and in the northwest it unconformably overlies Lower Orodovician submarine volcanics. These margins are intruded by cogenetic and younger granitoid rocks. The volcanic rocks form a calc-alkaline series, although gaps in silica content at 52–56, 67–68, and 73–74% separate them into four groups: basalts, andesites–dacites, rhyolites, and high-silica rhyolites.The high-silica rhyolites are chemically comparable to melts thought to form the upper parts of large, layered silicic magma chambers of epicontinental regions. Such an environment is also suggested by the large area of the Springdale caldera and the fact that it is one of a number of calderas that make up a large Silurian volcanic field in western Newfoundland. An epicontinental tectonothermal environment for central Newfoundland in Silurian–Devonian times is readily explained by the fact that this magmatic activity followed a period of destruction and closure of the early Paleozoic Iapetus Ocean, with trapped heat and basaltic magma causing large-scale melting of thickened and subducted continental crust in an overall transpressional tectonic regime.
2
Amanda, Fajar F., Ryoichi Yamada, Masaoki Uno, Satoshi Okumura, and Noriyoshi Tsuchiya. "Evaluation of Caldera Hosted Geothermal Potential during Volcanism and Magmatism in Subduction System, NE Japan." Geofluids 2019 (January 21, 2019): 1–14. http://dx.doi.org/10.1155/2019/3031586.
Full textAbstract:
Deep-seated geothermal reservoirs beneath calderas have high potential as sources of renewable energy. In this study, we used an analysis of melt inclusions to estimate the amount of water input to the upper crust and quantify the properties of a deep-seated geothermal reservoir within a fossil caldera, the late Miocene Fukano Caldera (formation age 8–6 Ma), Sendai, NE Japan. Our research shows that Fukano Caldera consists of the southern part and northern part deposits which differ in the age and composition. The northern deposits are older and have higher potassium and silica contents than the southern deposits. Both the northern and southern deposits record plagioclase and plagioclase–quartz differentiation and are classified as dacite–rhyolite. The fossil magma chamber underlying the caldera is estimated to have a depth of ~2–10 km and a water content of 3.3–7.0 wt.%, and when the chamber was active it had an estimated temperature of 750°C–795°C. The water input into the fossil magma chamber is estimated at 2.3–7.6 t/yr/m arc length based on the magma chamber size the water content in the magma chamber and the length of volcanism periods of Fukano Caldera, NE Japan arc. The total amount of water that is stored in the chamber is ~1014 kg. The chamber is saturated in water and has potential as a deep-seated geothermal reservoir. Based on the shape of the chamber, the reservoir measures ~10 km × 5 km in the horizontal dimension and is 7–9 km in vertical extent. The 0th estimate shows that the reservoir can hold the electric energy equivalent of 33–45 GW over 30 years of power generation. Although the Fukano reservoir has great potential, commercial exploitation remains challenging owing to the corrosive nature of the magmatic fluids and the uncertain permeability network of the reservoir.
3
Berg, Sylvia E., Valentin R. Troll, Chris Harris, Frances M. Deegan, Morten S. Riishuus, Steffi Burchardt, and Michael Krumbholz. "Exceptionally high whole-rock δ18O values in intra-caldera rhyolites from Northeast Iceland." Mineralogical Magazine 82, no. 5 (May 29, 2018): 1147–68. http://dx.doi.org/10.1180/mgm.2018.114.
Full textAbstract:
ABSTRACTThe Icelandic crust is characterized by low δ18O values that originate from pervasive high-temperature hydrothermal alteration by18O-depleted meteoric waters. Igneous rocks in Iceland with δ18O values significantly higher than unaltered oceanic crust (~5.7‰) are therefore rare. Here we report on rhyolitic intra-caldera samples from a cluster of Neogene central volcanoes in Borgarfjörður Eystri, Northeast Iceland, that show whole-rock δ18O values between +2.9 and +17.6‰ (n= 6), placing them among the highest δ18O values thus far recorded for Iceland. Extra-caldera rhyolite samples from the region, in turn, show δ18O whole-rock values between +3.7 and +7.8‰ (n= 6), consistent with the range of previously reported Icelandic rhyolites. Feldspar in the intra-caldera samples (n= 4) show δ18O values between +4.9 and +18.7‰, whereas pyroxene (n= 4) shows overall low δ18O values of +4.0 to +4.2‰, consistent with regional rhyolite values. In combination with the evidence from mineralogy and rock H2O contents, the high whole-rock δ18O values of the intra-caldera rhyolites appear to be the result of pervasive isotopic exchange during subsolidus hydrothermal alteration with18O-enriched water. This alteration conceivably occurred in a near-surface hot spring environment at the distal end of an intra-caldera hydrothermal system, and was probably fed by waters that had already undergone significant isotope exchange with the country rock. Alternatively,18O-enriched alteration fluids may have been produced during evaporation and boiling of standing water in former caldera lakes, which then interacted with the intra-caldera rock suites. Irrespective of the exact exchange processes involved, a previously unrecognized and highly localized δ18O-enriched rock composition exists on Iceland and thus probably within the Icelandic crust too.
4
Campbell, S. D. G., A. J. Reedman, M. F. Howells, and A. C. Mann. "The emplacement of geochemically distinct groups of rhyolites during the evolution of the Lower Rhyolitic Tuff Formation caldera (Ordovician), North Wales, U.K." Geological Magazine 124, no. 6 (November 1987): 501–11. http://dx.doi.org/10.1017/s0016756800017349.
Full textAbstract:
AbstractRhyolites in the vicinity of Snowdon (North Wales) are intimately associated with the evolution of the Lower Rhyolitic Tuff Formation (LRTF) caldera of Ordovician (Caradoc) age. They occur as deep-seated dykes, sills and small stocks, shallow-level intrusive domes, and domes extruded within a predominantly shallow-marine environment. Extrusion occurred during three main phases, indicating the episodic availability of rhyolite magma. The rhyolites can be divided on their trace element ratios (e.g. Nb/Zr) into five main groups. Extrusive representatives indicate that each group correlates strongly with a single phase of rhyolite extrusion. Within each group, the distribution and variation of intrusive form with stratigraphic level suggests that geochemically similar rocks were emplaced at approximately the same time. Consequently, the groups represent discrete magma compositions tapped from the evolving Snowdon subvolcanic magma system. Differences in distribution of the groups reflect changes in structural controls of emplacement before and after development of the LRTF caldera.
5
Saubin, E., B. Kennedy, H. Tuffen, A. R. L. Nichols, M. Villeneuve, I. Bindeman, A. Mortensen, et al. "Textural and geochemical window into the IDDP-1 rhyolitic melt, Krafla, Iceland, and its reaction to drilling." GSA Bulletin 133, no. 9-10 (January 6, 2021): 1815–30. http://dx.doi.org/10.1130/b35598.1.
Full textAbstract:
Abstract The unexpected intersection of rhyolitic magma and retrieval of quenched glass particles at the Iceland Deep Drilling Project-1 geothermal well in 2009 at Krafla, Iceland, provide unprecedented opportunities to characterize the genesis, storage, and behavior of subsurface silicic magma. In this study, we analyzed the complete time series of glass particles retrieved after magma was intersected, in terms of distribution, chemistry, and vesicle textures. Detailed analysis of the particles revealed them to represent bimodal rhyolitic magma compositions and textures. Early-retrieved clear vesicular glass has higher SiO2, crystal, and vesicle contents than later-retrieved dense brown glass. The vesicle size and distribution of the brown glass also reveal several vesicle populations. The glass particles vary in δD from −120‰ to −80‰ and have dissolved water contents spanning 1.3−2 wt%, although the majority of glass particles exhibit a narrower range. Vesicular textures indicate that volatile overpressure release predominantly occurred prior to late-stage magma ascent, and we infer that vesiculation occurred in response to drilling-induced decompression. The textures and chemistry of the rhyolitic glasses are consistent with variable partial melting of host felsite. The drilling recovery sequence indicates that the clear magma (lower degree partial melt) overlays the brown magma (higher degree partial melt). The isotopes and water species support high temperature hydration of these partial melts by a mixed meteoric and magmatic composition fluid. The textural evidence for partial melting and lack of crystallization imply that magma production is ongoing, and the growing magma body thus has a high potential for geothermal energy extraction. In summary, transfer of heat and fluids into felsite triggered variable degrees of felsite partial melting and produced a hydrated rhyolite magma with chemical and textural heterogeneities that were then enhanced by drilling perturbations. Such partial melting could occur extensively in the crust above magma chambers, where complex intrusive systems can form and supply the heat and fluids required to re-melt the host rock. Our findings emphasize the need for higher resolution geophysical monitoring of restless calderas both for hazard assessment and geothermal prospecting. We also provide insight into how shallow silicic magma reacts to drilling, which could be key to future exploration of the use of magma bodies in geothermal energy.
6
de Silva, S. L., J. Roberge, L. Bardelli, W. Báez, A. Ortiz, J. G. Viramonte, J. M. Arnosio, and R. Becchio. "Magmatic evolution and architecture of an arc-related, rhyolitic caldera complex: The late Pleistocene to Holocene Cerro Blanco volcanic complex, southern Puna, Argentina." Geosphere 18, no. 2 (January 25, 2022): 394–423. http://dx.doi.org/10.1130/ges02294.1.
Full textAbstract:
Abstract Through the lens of bulk-rock and matrix glass geochemistry, we investigated the magmatic evolution and pre-eruptive architecture of the siliceous magma complex beneath the Cerro Blanco volcanic complex, a Crater Lake–type caldera complex in the southern Puna Plateau of the Central Andes of Argentina. The Cerro Blanco volcanic complex has been the site of two caldera-forming eruptions with volcanic explosivity index (VEI) 6+ that emplaced the ca. 54 ka Campo Piedra Pomez ignimbrite and the ca. 4.2 ka Cerro Blanco ignimbrite. As such, it is the most productive recent explosive volcano in the Central Andes. The most recent eruptions (younger than 4.2 ka) are dominantly postcaldera effusions of crystal-rich domes and associated small explosive pulses. Previous work has demonstrated that andesitic recharge of and mixing with rhyolitic magma occurred at the base of the magma complex, at ~10 km depth. New isotopic data (Sr, Nd, Pb, and O) confirm that the Cerro Blanco volcanic complex rhyolite suite is part of a regional southern Puna, arc-related ignimbrite group. The suite defines a tight group of consanguineous siliceous magmas that serves as a model for the evolution of arc-related, caldera-forming silicic magma systems in the region and elsewhere. These data indicate that the rhyolites originated through limited assimilation of and mixing with upper-crustal lithologies by regional basaltic andesite parent materials, followed by extensive fractional crystallization. Least squares models of major elements in tandem with Rayleigh fractionation models for trace elements reveal that the internal variations among the rhyolites through time can be derived by extensive fractionation of a quartz–two feldspar (granitic minimum) assemblage with limited assimilation. The rare earth element character of local volumes of melt in some samples of the Campo Piedra Pomez ignimbrite basal fallout requires significant fractionation of amphibole. The distinctive major- and trace-element characteristics of bulk rock and matrix of the Campo Piedra Pomez and Cerro Blanco tephras provide useful geochemical fingerprints to facilitate regional tephrochronology. Available data indicate that rhyolites from other neighborhood centers, such as Cueros de Purulla, share bulk chemical characteristics with the Campo Piedra Pomez ignimbrite rhyolites, but they appear to be isotopically distinct. Pre-eruptive storage and final equilibration of the rhyolitic melts were estimated from matrix glass compositions projected onto the haplogranitic system (quartz-albite-orthoclase-H2O) and using rhyolite-MELTS models. These revealed equilibration pressures between 360 and 60 MPa (~10–2 km depth) with lowest pressures in the Holocene eruptions. Model temperatures for the suite ranged from 695 to 790 °C. Integrated together, our results reveal that the Cerro Blanco volcanic complex is a steady-state (low-magmatic-flux), arc-related complex, standing in contrast to the flare-up (high-magmatic-flux) supervolcanoes that dominate the Neogene volcanic stratigraphy. The silicic magmas of the Cerro Blanco volcanic complex were derived more directly from mafic and intermediate precursors through extensive fractional crystallization, albeit with some mixing and assimilation of local basement. Geochemical models and pressure-temperature estimates indicate that significant volumes of remnant cumulates of felsic and intermediate composition should dominate the polybaric magma complex beneath the Cerro Blanco volcanic complex, which gradually shallowed through time. Evolution to the most silicic compositions and final equilibration of some of the postcaldera domes occurred during ascent and decompression at depths less than 2 km. Our work connotes an incrementally accumulated (over at least 54 k.y.), upper-crustal pluton beneath the Cerro Blanco volcanic complex between 2 and 10 km depth. The composition of this pluton is predicted to be dominantly granitic, with deeper parts being granodioritic to tonalitic. The progressive solidification and eventual contraction of the magma complex may account for the decades of deflation that has characterized Cerro Blanco. The presently active geothermal anomaly and hydrothermal springs indicate the Cerro Blanco volcanic complex remains potentially active.
7
Barker, Simon J., Michael C. Rowe, Colin J. N. Wilson, John A. Gamble, Shane M. Rooyakkers, Richard J. Wysoczanski, Finnigan Illsley-Kemp, and Charles C. Kenworthy. "What lies beneath? Reconstructing the primitive magmas fueling voluminous silicic volcanism using olivine-hosted melt inclusions." Geology 48, no. 5 (February 27, 2020): 504–8. http://dx.doi.org/10.1130/g47422.1.
Full textAbstract:
Abstract Understanding the origins of the mantle melts that drive voluminous silicic volcanism is challenging because primitive magmas are generally trapped at depth. The central Taupō Volcanic Zone (TVZ; New Zealand) hosts an extraordinarily productive region of rhyolitic caldera volcanism. Accompanying and interspersed with the rhyolitic products, there are traces of basalt to andesite preserved as enclaves or pyroclasts in caldera eruption products and occurring as small monogenetic eruptive centers between calderas. These mafic materials contain MgO-rich olivines (Fo79–86) that host melt inclusions capturing the most primitive basaltic melts fueling the central TVZ. Olivine-hosted melt inclusion compositions associated with the caldera volcanoes (intracaldera samples) contrast with those from the nearby, mafic intercaldera monogenetic centers. Intracaldera melt inclusions from the modern caldera volcanoes of Taupō and Okataina have lower abundances of incompatible elements, reflecting distinct mantle melts. There is a direct link showing that caldera-related silicic volcanism is fueled by basaltic magmas that have resulted from higher degrees of partial melting of a more depleted mantle source, along with distinct subduction signatures. The locations and vigor of Taupō and Okataina are fundamentally related to the degree of melting and flux of basalt from the mantle, and intercaldera mafic eruptive products are thus not representative of the feeder magmas for the caldera volcanoes. Inherited olivines and their melt inclusions provide a unique “window” into the mantle dynamics that drive the active TVZ silicic magmatic systems and may present a useful approach at other volcanoes that show evidence for mafic recharge.
8
Ewart, A., R. W. Schon, and B. W. Chappell. "The Cretaceous volcanic-plutonic province of the central Queensland (Australia) coast—a rift related ‘calc-alkaline’ province." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 83, no. 1-2 (1992): 327–45. http://dx.doi.org/10.1017/s0263593300008002.
Full textAbstract:
ABSTRACTSilicic and minor intermediate and mafic pyroclastics, lavas, and dykes occupy a NW-trending zone through the Whitsunday, Cumberland and Northumberland Island groups, and locally areas on the adjacent mainland, over a distance of more than 300 km along the central Queensland coast. K-Ar and Rb-Sr data indicate an age range of 95–132 Ma, with the main activity approximately between 105–120 Ma; there is, however, evidence for easterly increasing ages. Comagmatic granites, some clearly intrusive into the volcanics, occur together with two localised areas of Triassic potassic granites (229 Ma), that form the immediate basement.The volcanics are dominantly rhyolitic to dacitic lithic ignimbrites, with intercalated surge and bedded tuffs, accretionary lapilli tuffs, and lag deposits. Associated rock types include isolated rhyolitic and dacitic domes, and volumetrically minor andesite and rare basalt flows. The sequence is cut by abundant dykes, especially in the northern region and adjacent mainland, ranging from dolerite through andesite, dacite and rhyolite. Dyke orientations show maxima between NW-NNE. Isotope data, similarities in petrography and mineralogy, and alteration patterns all suggest dyke intrusion to be broadly contemporaneous with volcanism. The thickness of the volcanics is unconstrained, although in the Whitsunday area, minimum thicknesses of >1 km are inferred. Eruptive centres are believed to occur throughout the region, and include at least two areas of caldera-style collapse. The sequences are thus considered as predominantly intracaldera.The phenocryst mineralogy is similar to modern “orogenic” volcanics. Phases include plagioclase, augite, hypersthene (uralitised), magnetite, ilmenite, with less common hornblende, and even rarer quartz, sanidine, and biotite. Fe-enriched compositions only develop in some high-silica rhyolites. The granites range from quartz diorite to granite s.s., and some contain spectacular concentrations of partially disaggregated dioritic inclusions.Chemically, the suite ranges continuously from basalt to high-silica rhyolite, with calc-alkali to high-K affinities, and geochemical signatures similar to modern subduction-related magmas. Only the high-silica rhyolites and granites exhibit evidence of extensive fractional crystallisation (e.g. pronounced Eu anomalies). Variation within the suite can only satisfactorily be modelled in terms of two component mixing, with superimposed crystal fractionation. Nd and Sr isotope compositions are relatively coherent, with εNd + 2·2 to +7·3, and ISr (calculated at 110 and 115 Ma) 0·7031-0·7044. These are relatively primitive, and imply mantle and/or newly accreted crustal magma sources.The two end-members proposed are within-plate tholeiitic melt, and ?low-silica rhyolitic melts generated by partial fusion of Permian (to ?Carboniferous) arc and arc basement. The arc-like geochemistry is thus considered to be source inherited. The tectonic setting for Cretaceous volcanism is correlated with updoming and basin rifting during the early stages of continental breakup, culminating in the opening of the Tasman Basin. Cretaceous volcanism is also recognised in the Maryborough Basin (S Queensland), the Lord Howe Rise, and New Caledonia, indicating the regional extent of volcanism associated with the complex breakup of the eastern Australasian continent margin.
9
Swanson, Eric. "History of Field Observations on Volcanic Rocks of Western Mexico, Pre-Columbian to Recent." Earth Sciences History 30, no. 1 (December 1, 2011): 106–34. http://dx.doi.org/10.17704/eshi.30.1.p68hl442l6w11036.
Full textAbstract:
By the time the first detailed reports on western Mexico's volcanic rocks had begun to appear in the 1970s, most of the earlier observations on these rocks and most knowledge of those who made these observations were all but forgotten. A review of previous field observations in this region shows, however, a long history of geologic discovery reflecting or even preceding developments elsewhere.Ethnological studies suggest that the Pre-Columbian inhabitants of the Sierra Madre Occidental (SMO) observed the characteristics of rock formations in their sierra homeland and understood something of the regional stratigraphic relationships. Late sixteenth and early seventeenth century explorers of the Spanish Colonial Period singled out volcanic rock known to them as piedra de malpaís for special recognition, and Padre Kino and his fellow explorers clearly recognized the volcanic origin of piedra de malpaís decades prior to similar observations in Europe. As the Spanish Colonial Period came to a close, Andrés Manuel del Río help organize a state-of-theart mining college in Mexico City where students were instructed in Werner's geognosy prior to their taking positions in Mexico's mining industry, most of it located in western Mexico's volcanic rocks.Although the first part of the tumultuous period between Mexico's revolutions of 1810 and 1910 saw few advances in geological knowledge, the reign of President Porfirio Díaz produced a geologic map of Mexico, the founding of the Instituto de Geología, and an ‘American invasion’ of geologists and mining engineers who locally gathered information on the nature of volcanic rocks of western Mexico. During the same period, Instituto geologist Ezequiel Ordóñez established the general stratigraphic sequence in the SMO, recognized the widespread occurrence of rhyolite there, and applied the petrographic microscope to the study of SMO volcanic rocks. The first identification of ignimbrites in the SMO came as a result of the World War II-era search for strategic minerals, and NASA's push to put a man on the Moon supported a series of student mapping projects producing the SMO's first geologic maps showing individual ignimbrite units and calderas.
10
Juliani, Caetano, Rafael Rodrigues de Assis, Lena Virgínia Soares Monteiro, Carlos Marcello Dias Fernandes, José Eduardo Zimmermann da Silva Martins, and Jhoseph Ricardo Costa e Costa. "Gold in Paleoproterozoic (2.1 to 1.77 Ga) Continental Magmatic Arcs at the Tapajós and Juruena Mineral Provinces (Amazonian Craton, Brazil): A New Frontier for the Exploration of Epithermal–Porphyry and Related Deposits." Minerals 11, no. 7 (July 1, 2021): 714. http://dx.doi.org/10.3390/min11070714.
Full textAbstract:
This review paper aims to integrate geological, tectonic and metallogenetic data, including new data, and propose a regional model for the gold (and base metal) mineralization in the south Amazonian Craton to support the mineral exploration concerning magmatic–hydrothermal deposits. The Proterozoic evolution of the Amazonian Craton comprises the accretion of terrains to the Archean Carajás Mineral Province. In the Tapajós and Juruena mineral provinces, located at the south part of the Amazonian craton, a long-lived ocean–continent subduction event produced ca. 2.0 to 1.77 Ga continental magmatic arcs. Extensive lava flows, volcaniclastic, sedimentary, and plutonic rocks were originated during at least four major orogenic magmatic events (ca. 2.1, 1.9, 1.88, and 1.80 Ga) and two post- to anorogenic events (ca. 1.87 and 1.77 Ga). Gold mineralization occurs in: (i) alluvial/colluvial occurrences, (ii) orogenic carbonate–sulfide-rich quartz veins in shear zones, (iii) stockworks, veins, and dissemination in granites, (iv) contact of basic dikes, (v) well-preserved high-, intermediate- and low-sulfidation epithermal mineralization, and (vi) porphyry-like and intrusion-related gold systems associated with late- to post-orogenic epizonal granites. The estimated historical gold production, mainly in secondary deposits, is over 27 Moz at the Tapajós and 6 Moz at the Juruena provinces. A total resource of over 5 Moz Au is currently defined in several small to large primary gold deposits. Andesite to rhyolite, volcaniclastic, and clastic sedimentary rocks (1.96–1.88 Ga) host epithermal (high-, intermediate-, and low-sulfidation) Au–(Ag–Pb–Zn) mineralization, whereas Au–Cu and Cu–M–Au mineralization is hosted in sub-volcanic tonalitic to granitic plutons. Advanced argillic alteration (alunite, pyrophyllite, enargite) associated with high-sulfidation mineralization occurs in ring volcanoes around nested volcanic calderas. This zone grades outward to propylitic or chlorite alteration, often covered by silica caps with vuggy silica. Lava flows and volcaniclastic rocks within faults or associated with volcanic edifices and rhyolitic domes host low- and intermediate-sulfidation mineralization. Low-sulfidation alteration zones typically have adularia and illite or sericite. Chalcopyrite, sphalerite, galena, pyrite, digenite, and manganiferous calcite are related to intermediate-sulfidation gold mineralization. Late- to post-orogenic evolved oxidized I-type granitoids host alkalic-type epithermal and porphyry-like gold mineralization. Porphyry-style hydrothermal alteration is analogous to those of modern systems, with inner sodic and potassic (potassic feldspar ± biotite or biotite) alterations grading to propylitic, muscovite-sericite, chlorite–sericite, and chlorite alterations. Potassic alteration zones are the locus of Cu–Mo mineralization, and gold-rich zones occur in muscovite/sericite–quartz–pyrite alteration. The Paleoproterozoic epithermal and porphyry-like mineralization in these large provinces defines a new frontier for the exploration of world-class gold deposits in the worldwide Proterozoic arc-related magmatic terrains.
Dissertations / Theses on the topic "Rhyolite calderas"
1
Marcy, Phillip Ira. "Revisiting Volcanology and Composition of Rhyolites and Associated REE Rich Mafic Clasts of the Three Fingers Caldera, SE Oregon." PDXScholar, 2014. https://pdxscholar.library.pdx.edu/open_access_etds/1543.
Full textAbstract:
Two adjacent caldera systems, the Mahogany Mountain and the Three Fingers caldera constitute voluminous rhyolitic volcanic deposits on the eastern margin of the Oregon-Idaho graben during the middle-Miocene. Both calderas are part of the Lake Owyhee volcanic field that in turn is part of widespread rhyolite deposits associated with the Columbia River Basalt province. We focus on establishing relationships between intracaldera units of Three Fingers caldera and caldera-forming tuff of Spring Creek and surveying the distribution of entrained mafic clasts which often display anomalous concentrations of rare earth elements.
Previous mapping identified two intra-caldera facies and one outflow facies of the tuff of Spring Creek, in addition to a younger rhyolite within the caldera (Trp). New 40Ar/39Ar dates show these units are nearly time equivalent at 15.64 ± 0.08 Ma for Trp and 15.64 ± 0.09 Ma for tuff of Spring Creek. Field evidence shows extensive coverage of Trp and associated facies emplaced after a period of sedimentation within the caldera. The main reinterpretations are: i) the mostly devitrified units of Trp are time equivalent to flows and domes of glassy, vesicular, or brecciated rhyolite previously mapped as intra-caldera tuff of Spring Creek; and ii) mafic clasts present in dense glass and porous rhyolite are fragments of mafic lava flows entrained by the subsequent eruptions.
New geochemical and mineralogical evidence clearly distinguish the outflow tuff of Spring Creek and intracaldera rhyolites. Compared to the outflow tuff, intracaldera rhyolite flows are less Fe-rich, (2 vs. 3 wt.% FeO), and higher silica (77 vs. 74 wt.% SiO2) rhyolites that lack vitrophyric texture. I interpret the investigated area as a rhyolite dome field, erupted subsequent to caldera collapse. The proximity of vents resulted in a complex stratigraphic overlap of rhyolite flows and clastic debris issued from coalescing domes. The predominance of high-standing dome interiors reflects the more resistant nature of dense devitrified rhyolite as compared to pumiceous, glassy, or brecciated facies of intra-caldera rhyolite.
Enrichment of REE in mafic clasts is highly variable, and does not correlate with their entrainment in a specific facies of intra-caldera rhyolite. Individual clasts contain up to 2400 ppm Nd, 1800 ppm Ce, and 1400 ppm La in the most enriched samples. Linear regression shows these highly anomalous concentrations are not correlated with variations in major element chemistry between enriched and un-enriched clasts. The geographic extent of mafic clast-bearing units is limited to less than 5 percent of the area mapped, and their distribution within these units is typically volumetrically insignificant, limiting their economic potential. Mechanisms for enrichment of REE within these rocks is however significant to our understanding of a yet unexplained phenomenon and may lead to further discoveries with greater economic potential.
2
Brown, Elizabeth Ann. "Rhyolite Petrogenesis at Tower Mountain Caldera, OR." PDXScholar, 2017. https://pdxscholar.library.pdx.edu/open_access_etds/3997.
Full textAbstract:
Tower Mountain Caldera is the main feature of an Oligocene volcanic field located in the Umatilla National Forest, eastern Oregon. It is perfectly suited to investigate models of rhyolite petrogenesis as all of the important rock components for evaluating generation models are present in a single location and thus are presumably related; basalts, intermediate igneous rocks (which consist of older plutons and younger volcanic rocks, which are ~coeval with rhyolites), metamorphic basement rocks of significant grade, and rhyolites of varying composition. The formation of the caldera produced the Dale Tuff, which comprises the intra-caldera and outflow facies. 40Ar/39Ar dating places the age of the tuff at 32.66 ± 0.36 Ma. Post-caldera rhyolites erupted along apparent ring fractures and elsewhere. Radiometric U-Pb dating of zircons from three of these rhyolites yielded ages of 32.167 ± 0.020 Ma (#CH07a), 31.798 ± 0.012 Ma (#TM5), and 31.426 ± 0.016 Ma (#CH08a). All rhyolites at Tower Mountain range from low to high silica varieties. Some of the post-caldera rhyolites are chemically similar to the Dale Tuff, such as sample CH07a, and have compositions typical of rhyolites of calc-alkaline volcanic centers (I-type rhyolites), while others are similar to A-type rhyolites (CH08a and TM5). The ages indicate that the calc-alkaline rhyolites were followed by the A-type rhyolites. The petrogenetic relationships between the various rocks types were evaluated. Partial melt modeling based on experimental melts produced from crustal material indicates that batch partial melting of metamorphosed high silica crustal material modified by the addition of more primitive mafic material by assimilation/contamination is the most likely source for the Tower Mountain rhyolites.
3
Watts, Kathryn Erin 1983. "Large-Volume Rhyolite Genesis in Caldera Complexes of the Snake River Plain." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/11565.
Full textAbstract:
xix, 189 p. : ill. (some col.), maps (some col.)Caldera-forming eruptions are dramatic and destructive natural phenomena, causing severe and sustained consequences to society. This dissertation presents new geochemical and geochronologic data for caldera-forming tuffs and pre- and post-caldera rhyolites of the two youngest caldera complexes in the Snake River Plain (SRP) in the western USA: Heise (6.6-4.5 Ma) and Yellowstone (2.1-0.6 Ma). Caldera complex evolution at Heise and Yellowstone can be described by formation of 3-4 spatially overlapping "nested" calderas, successive collapse of intracaldera fill, and development of a large hydrothermal system. Comparison between Heise and Yellowstone reveals that late-stage rhyolite eruptions have drastic depletions in 18 O that require remelting of large volumes (1,000's of km 3 ) of hydrothermally altered rock. Archean xenoliths and Phanerozoic rocks of the crustal basement beneath the SRP province are not depleted in 18 O and therefore cannot be a source of these rhyolites. Isotopic mixing models indicate that early large-volume rhyolites are produced by melting and hybridization of the crust by mantle-derived basalt, and late-stage rhyolites tap hydrothermally altered portions of intracaldera rocks from previous eruptions. Caldera-forming eruptions at Heise culminated 4.45 Ma with eruption of the 1,800 km 3 Kilgore Tuff, the most voluminous 18 O-depleted rhyolite in the SRP and worldwide. O, Sr, and Nd isotope geochemistry, zircon ages, mineral and whole-rock geochemistry, and liquidus temperatures for Kilgore Tuff samples erupted >100 km apart are similar and/or overlapping within error, indicating derivation from a remarkably homogeneous low-δ 18 O magma reservoir (δ 18 O=3.4[per thousand]). Caldera-wide batch assembly and homogenization of variably 18 O-depleted melt pockets with diverse zircon populations can explain the Kilgore Tuff's genesis. Central Plateau Member (CPM) rhyolites at Yellowstone have the same timing (∼2 million years after the initiation of volcanism), magnitude of δ 18 O depletion (∼3[per thousand] depleted relative to normal rhyolites), and cumulative eruptive volume (∼4,000-4,500 km 3 ) as the Kilgore Tuff of the Heise volcanic field. Isotopic, age, and geochemical data for CPM rhyolites show that they become progressively more homogeneous and evolved from 260 ka to 75 ka. Whereas the Kilgore Tuff erupted climactically as an explosive caldera-forming tuff, CPM rhyolite eruptions record sequential, predominantly effusive, "snapshots" of magma assembly, homogenization, and differentiation. This dissertation includes co-authored materials both previously published and submitted for publication.
Committee in charge: Ilya Bindeman, Chairperson; Gregory Retallack, Member; Mark Reed, Member; W. Andrew Marcus, Outside Member
4
Ashwell, Paul. "Controls on rhyolite lava dome eruptions in the Taupo Volcanic Zone." Thesis, University of Canterbury. Geological Sciences, 2014. http://hdl.handle.net/10092/8965.
Full textAbstract:
The evolution of rhyolitic lava from effusion to cessation of activity is poorly understood. Recent lava dome eruptions at Unzen, Colima, Chaiten and Soufrière Hills have vastly increased our knowledge on the changes in behaviour of active domes. However, in ancient domes, little knowledge of the evolution of individual extrusion events exists. Instead, internal structures and facies variations can be used to assess the mechanisms of eruption.
Rhyolitic magma rising in a conduit vesiculates and undergoes shear, such that lava erupting at the surface will be a mix of glass and sheared vesicles that form a permeable network, and with or without phenocryst or microlites. This foam will undergo compression from overburden in the shallow conduit and lava dome, forcing the vesicles to close and affecting the permeable network. High temperature, uniaxial compression experiments on crystal-rich and crystal-poor lavas have quantified the evolution of porosity and permeability in such environments. The deformation mechanisms involved in uniaxial deformation are viscous deformation and cracking. Crack production is controlled by strain rate and crystallinity, as strain is localised in crystals in crystal rich lavas. In crystal poor lavas, high strain rates result in long cracks that drastically increase permeability at low strain. Numerous and small cracks in crystal rich lavas allow the permeable network to remain open (although at a lower permeability than undeformed samples) while the porosity decreases.
Flow bands result from shear movement within the conduit. Upon extrusion, these bands will become modified from movement of lava, and can therefore be used to reconstruct styles of eruption. Both Ngongotaha and Ruawahia domes, from Rotorua caldera and Okataina caldera complex (OCC) respectively, show complex flow banding that can be traced to elongated or aligned vents. The northernmost lobe at Ngongotaha exhibits a fan-like distribution of flow bands that are interpreted as resulting from an initial lava flow from a N – S trending fissure. This flow then transitioned into intrusion of obsidian sheets directly above the conduit, bound by wide breccia zones which show vertical movement of the sheets. Progressive intrusions then forced the sheets laterally, forming a sequence of sheets and breccia zones. At Ruawahia, the flow bands show two types of eruption; long flow lobes with ramp structures, and smaller spiny lobes which show vertical movement and possible spine extrusion. The difference is likely due to palaeotopography, as a large pyroclastic cone would have confined the small domes, while the flow lobes were unconfined and able to flow down slope. The vents at Ruawahia are aligned in a NE – SW orientation. Both domes are suggested to have formed from the intrusion of a dyke.
The orientations of the alignment or elongation of vents at Ngongotaha and Ruawahia can be attributed to the overall regional structure of the Taupo Volcanic Zone (TVZ). At Ngongotaha, the N – S trending elongated vent is suggested to be controlled by a N – S trending caldera collapse structure at Rotorua caldera. The rest of the lobes at Ngongotaha, as well as other domes at Rotorua caldera, are controlled by the NE – SW trending extensional regional structure or a NW – SE trending basement structure. The collapse of Rotorua caldera, and geometry of the deformation margin, are related to the interplay of these structures. At Ruawahia, the NE – SW trending vent zone is parallel to the regional extension across the OCC, as shown by the orientation of intrusion of the 1886AD dyke through the Tarawera dome complex.
The NE – SW trending regional structures observed at both Rotorua caldera and Okataina caldera complex are very similar to each other, but differ from extension within the Taupo rift to the south. Lava domes, such as Ngongotaha, that are controlled by this structure show that the ‘kink’ in the extension across Okataina caldera complex was active across Rotorua caldera during the collapse at 240 ka, and possibly earlier.
This study shows the evolution of dyke-fed lava domes during eruption, and the control of regional structures in the location and timing of eruption. These findings improve our knowledge of the evolution of porosity and permeability in a compacting lava dome, as well as of the structures of Rotorua caldera, the longevity of volcanic activity at dormant calderas and the hazard potential of dyke-fed lava domes.
5
Shipley, Niccole Kiyomi. "Isotopic and Petrologic Investigation and Model of Genesis of Large-Volume High-Silica Rhyolites in Arc Environments: Karymshina Caldera, Kamchatka, Russia." Thesis, University of Oregon, 2011. http://hdl.handle.net/1794/12187.
Full textAbstract:
xii, 76 p. ： ill. (some col.)Large-volume calderas are responsible for producing large deposits of rhyolite and high-silica rhyolite, but the mechanisms by which these deposits are produced are still poorly understood. The Kamchatka Peninsula of Russia contains several large calderas and is one of the most volcanically active areas on Earth. Karymshina Caldera, the largest (25 km x 15 km) caldera in Kamchatka, produced an estimated 800 km 3 of high-silica rhyolitic ignimbrites and post-caldera extrusions, which erupted 1.78 and 0.5-0.8 Ma, respectively. SiO2 content ranges from 66.27-71.89 wt% in the ignimbrites and 70.16-77.70 wt% in the post-caldera extrusions studied. Crystal content is primarily quartz and plagioclase, 0.5-2 mm in size, with other minerals. Values of δ18 O, δD, 87 Sr/86 Sr, and 144 Nd/143 Nd indicate little assimilation of crustal material, in contrast to modeling results. XRF analysis indicates a homogeneous magma. The rhyolite-MELTS program was used to model crystallization of a basaltic source with addition of amphibolite partial melt and hydrothermally-altered silicic rock to reproduce the observed compositions. This thesis contains both previously published and co-authored material.
Committee in charge: Dr. Ilya Bindeman， Chairperson； Dr. Paul Wallace， Member； Dr. Mark Reed， Member
6
Drew, Dana. "An Isotopic, Trace Element, and Volatile Investigation of Large-Volume Rhyolite Generation at the Picabo Volcanic Field of the Yellowstone Hotspot Track." Thesis, University of Oregon, 2014. http://hdl.handle.net/1794/17894.
Full textAbstract:
Rhyolites of the Picabo volcanic field (10.4-6.6 Ma) of the Yellowstone hotspot in eastern Idaho are preserved as thick ignimbrites and lavas along the margins of the Snake River Plain. This study presents new O and Hf isotope data and U-Pb geochronology from individual zircons, O isotope data from major phenocrysts, whole rock Sr and Nd isotope data, whole rock geochemistry, and trace element and volatile analyses of quartz-hosted melt inclusions, which were used to characterize the evolution of rhyolite generation through the eruptive sequence. The chemical composition of the first eruption of the caldera complex, the Tuff of Arbon Valley, suggests magma generation through repeated magma injection into the crust, remelting, crystallization, mixing, and crustal assimilation. Subsequent eruptions have diverse and low δ18O signatures indicating rhyolite generation through the remelting of variably hydrothermally altered volcanics, followed by rapid batch assembly.
This thesis includes co-authored material previously published.
7
Girard, Guillaume. "The dynamics of post-collapse magmatism at rhyolitic calderas: analogue experiments and geochemistry of Yellowstone lavas." Thesis, McGill University, 2009. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=40738.
Full textAbstract:
The dynamics of magma replenishment in silicic magma reservoirs are not well understood. This is an important issue, since replenishment may lead to the rapid accumulation of large volumes of crystal-poor magma, a condition potentially leading to cataclysmic caldera-forming eruptions. To shed light on this process, I have undertaken a combined experimental – geochemical approach designed to provide an integrated and synthetic view of magma replenishment processes. Scaled analogue experiments show that in silicic systems, buoyant injections rise through a magma reservoir without significant mixing with resident material, forming a layered reservoir. When a crystal mush is present at the base of the reservoir, its presence does not hinder buoyant injections to ascend. Indeed, such injections entrain crystals from the mush and transport them to the uppermost layers of the reservoir, resulting in the accumulation of a mix of replenishing magma and mush crystals. This process may have played a significant role in the generation of early post-collapse rhyolites of Yellowstone caldera, the Upper Basin Member rhyolites. In these lavas, I observe the coexistence of large, isolated, sieved plagioclase crystals with small, fresh, more calcic plagioclase crystals occurring as aggregates with pyroxenes and oxides. This unusual mineral assemblage suggests that a higher-temperature, more primitive silicic replenishing magma mixed with crystals from a mush shortly before eruption. In this scenario, the aggregates crystallized from the replenishing magma while the sieved crystals were extracted from the mush. Unlike the Upper Basin Member rhyolites, the younger voluminous Central Plateau Member rhyolites define a cogenetic series in which younger lavas exhibit more evolved mineralogy and trace element signatures, while crystal geochemistry suggests crystallization from progressively cooler melts. At the same time, the crystals also exhibit dissolution textures, suggesting a rehLa dynamique des recharges magmatiques dans les réservoirs de magma silicique est assez mal comprise. Ceci est un problème important, puisque les recharges magmatiques peuvent entraîner l’accumulation rapide de grands volumes de magma pauvre en cristaux, une configuration susceptible d’évoluer vers une éruption cataclysmique et la formation d’une caldeira. Pour comprendre ce processus, j’ai mené une approche combinant expériences et géochimie, afin d’obtenir une vision intégrée et synthétique du processus de recharges magmatiques. Des expériences analogiques dimensionnées montrent que, pour les systèmes siliciques, des injections de magma moins dense montent dans un réservoir magmatique sans se mélanger de façon significative avec le magma du réservoir, et forment un réservoir zoné. Lorsqu’un niveau saturé en cristaux est présent à la base du réservoir, sa présence n’empêche pas l’ascension des injections. En effet, ces injections moins denses arrachent des cristaux à ce niveau et les entraînent vers le toit du réservoir, où se forme une couche constituée d’un mélange du nouveau magma et de cristaux de la base du réservoir. Ce mécanisme a probablement joué un rôle clé dans la génèse des rhyolites post-caldeira précoces à Yellowstone, les rhyolites d’Upper Basin Member. Dans ces laves, j’observe une coexistence de grands cristaux de plagioclase isolés portant des textures en tamis, et de petits cristaux de plagioclase frais, plus calciques, présents en aggrégats avec des pyroxènes et des oxydes. Cette association inhabituelle suggère qu’un magma silicique plus primitif et plus chaud s’est mélangé à des cristaux d’un réservoir magmatique riche en cristaux peu avant son éruption. Dans ce modèle, les aggrégats ont cristallisé depuis le nouveau magma, et les cristaux à textures en tamis ont été arrachés au réservoir cristallin. Par opposition aux rhyolites d’Upper Basin Member, le
8
Chabiron, Aliouka. "Les gisements d'uranium de la caldeira de Streltsovka (Transbaikalie, Russie)." Nancy 1, 1999. http://www.theses.fr/1999NAN10069.
Full textAbstract:
Les gisements d'u et mo de streltsovka (Russie), représentent les plus grandes ressources en u du monde associées a des volcanites (200000 tu). Les inclusions vitreuses des phénocristaux de quartz, ont permis de caractériser le magma rhyolitique avant tout phénomène d'altération. Il est per alcalin (1. 04 < (k+na)/al < 1. 10), riche en f (1. 4-2. 7%), pauvre en cl (0. 2%). Il est pauvre en h 2o (1. 9 0. 6%), riche en u (15-23 ppm), th (33-49 ppm). L'analyse des éléments traces et des terres rares a la microsonde ionique à montre qu'il est enrichi en y et nb, caractéristiques des magmas alcalins très fractionnés. En considérant 7 ppm d'u dans les rhyolites altérées et 17 ppm dans le magma initial, l'altération hydrothermale de 1 km 3 de rhyolite libère 26000 tu. Une efficacité de 25% du processus de dépôt d'u a partir des solutions hydrothermales ayant altère l'ensemble rhyolitique peut expliquer la totalité des réserves d'u des gisements. Dans le socle granitique, l'étude minéralogique et géochimique montre que les granodiorites, les granites porphyroïdes et les granites a biotite peuvent appartenir a une même suite magmatique subalcaline sodi-potassique. Le leuco granite profond montre une typologie alcaline du fait de ses teneurs élevées en sio 2 (75. 6-77. 2%), na 2o+k 2o (8. 4-8. 9%), nb (12-28 ppm), y (70-94 ppm), th (32-53 ppm), de ses faibles teneurs en ba (10-20 ppm), sr (6-16 ppm). L'altération hydrothermale très importante des granites subalcalins et alcalins de streltsovka montre que l'u, difficilement lessivable dans les minéraux accessoires, a été toutefois libéré. Un calcul de bilan de masse montre qu'1 km 3 de granite peut libérer 650 tu lors de l'altération de l'allanite. Cette estimation est minimale car le fluide oxydant ayant mobilise l'u de l'allanite a pu dissoudre les autres porteurs d'u éventuellement présents dans les granites, tels que l'uraninite.
9
Briot, Danielle. "Génèse d'une série alcaline intraplaque continentale : étude géochimique (éléments traces et isotopes SR-ND-O) du volcan des Monts Dore (Massif central français)." Clermond-Ferrand 2, 1988. http://www.theses.fr/1988CLF21107.
Full textAbstract:
Le stratovolcan des Mont Dore (massif central français) est caractérisé par l'existence d'une caldera, par l'abondance des laves de composition globalement intermédiaire trachyandesitique et par la coexistence de laves sur- et sous-saturées. Il s'est édifié en deux temps. De 3 a 1;5 ma, l'activité se concentre au niveau des volcans septentrionnaux (Mont Dore s. S. , d'ordanche, aiguiller). Cette période est marquée par l'effondrement de la caldera de la haute-Dordogne et l'émission de rhyolites (ponces rhyolitiques de la grande nappe, dôme de la Gacherie. . . ). De 0;9 a 0;25 ma, le volcan du Sancy puis le massif adventif s'édifient au sud des structures précedentes. L'étude géochimique (isotopes du sr, du nd et de l'oxygène associes aux éléments en trace) des basaltes s. L. Met en évidence une évolution par cristallisation fractionnée d'olivine et de clinopyroxenes (+ ou - opaques) depuis les basanites jusqu'aux hawaiites. Les laves trachyandesitiques hétérogènes sont marquées par des déséquilibres minéralogiques, des phénomènes complexes de brassage mécanique de magmas, associés à l'assimilation de xenocristaux, de cumulats, de roches subvolcaniques et de socle. L'expulsion de fluides et des liquides résiduels lors de la cristallisation plus ou moins rapide des inclusions comagmatiques basiques et postérieurement à leur incorporation dans un magma trachytisque joue un rôle important dans la genèse d'inclusions particulières, préalablement interprérees comme des "liquides fractionnés". Au vu des données isotopiques, les trachyandesites basiques ne peuvent être le résultat d'un simple mélange abouti entre deux magmas. L'abondance des trachyandesites ne serait qu'un artefact dû aux processus de brassage mécanique de magmas de realimentation périodique des réservoirs magmatiques. Les données isotopiques sur les ponces et dômes rhyolitiques (**(87)sr/**(86)sr et **(143)nd/**(144)nd) excluent une origine par anatexie généralisée de la croute granitique mais montrent l'existence d'une contamination par la croute granito-gneissique. Les trachyphonolites et phonolites sont issus de la cristallisation fractionnée d'amphibole, de sphène et de feldspath potassique a partir des basanites et tephrites. Un modèle évolutif de réservoir magmatique dans la croute supérieure est proposé en fonction de l'âge, de la nature et de la répartition spatiale des produits émis en surface. A partir de quelques données géochimiques sur les peridotites et les basaltes du massif central et des données géophysiques disponibles, des esquisses de manteau sous cette région volcanisée sont également proposées
10
Martinez, Serrano Raymundo Gerardo. "Caractérisation minéralogique, géochimique et isotopique du champ géothermique de Los Humeros, Mexique : interactions fluide-roche dans un système à fluide mixte (eau-vapeur)." Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL003N.
Full textAbstract:
Le champ géothermique de Los Humeros se localise dans un centre volcanique complexe du type caldera, d'âge tertiaire-récent. Le but de ce travail est d'établir les conditions de formation des minéraux d'altération, leur corrélation avec l'existence des fluides mixtes actuels (eau-vapeur) et leur comportement à travers le temps. Ce travail est divisé en quatre parties. La première partie est consacrée à l'étude pétrographique et chimique des formations volcaniques du site, ainsi qu'a la caractérisation des principaux minéraux d'altération. Il existe une intercalation d'andésites et de rhyolites, avec une distribution des altérations en fonction de la température, de la roche et du fluide. Dans la deuxième partie, nous voyons que les divers géothermomètres cationiques indiquent que la température du réservoir varie de 280 à 310c, mais que la concentration des cations d'alcalin met en évidence l'absence d'équilibre chimique eau-roche, donc il existe un mélange des fluides et un excès de vapeur très important. La troisième partie est consacrée à l'étude cristallochimique des phases d'altération. Ainsi, la chimie des altérations est comparable à celle des autres systèmes géothermiques, mais la variation de certains éléments chimiques est une fonction de la température, de la fugacité de l'oxygène et du type de roche. La dernière partie montre que la composition isotopique du soufre des pyrites hydrothermales est comparable à celle des fluides actuels, mais avec des variations locales en fonction des conditions physicochimiques des fluides
Book chapters on the topic "Rhyolite calderas"
1
Ronald Sides, J., M. E. Bickford, R. D. Shuster, and R. L. Nusbaum. "Calderasin The Precambriante Rrane of the ST. Francois Mountains, Southeastern Missouri." In 1989, Granites and Rhyolites, 10349–64. Washington, DC: American Geophysical Union, 2013. http://dx.doi.org/10.1002/9781118782057.ch13.
Full text
2
Busby-Spera, Cathy J. "Large-Volume Rhyolite Ash Flow Eruptions and Submarine Caldera Collapse in the Lower Mesozoic Sierra Nevada, California." In Collected Reprint Series, 8417–27. Washington, DC: American Geophysical Union., 2014. http://dx.doi.org/10.1002/9781118782095.ch15.
Full text
3
Hildreth, Wes, Robert L. Christiansen, and Jamesr R. O'Neil. "Catastrophic Isotopic Modification of Rhyolitic Magma at Times of Caldera Subsidence, Yellowstone Pelateau Volcanic Field." In Collected Reprint Series, 8339–69. Washington, DC: American Geophysical Union., 2014. http://dx.doi.org/10.1002/9781118782095.ch11.
Full text
4
Michelfelder*, Gary S. "Petrology and volcanology of the Mesoproterozoic igneous rocks of the Saint Francois Mountains terrane, southeast Missouri, USA." In Field Excursions from the 2021 GSA Section Meetings, 253–89. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.0061(11).
Full textAbstract:
ABSTRACT The Saint Francois Mountains are the physiographic expression of the central part of the Ozark Dome of southeastern Missouri. The mountains are made up of a quaquaversal-dipping series of Paleozoic units cored by the Mesoproterozoic-aged rocks of the broader Saint Francois Mountains terrane. The Saint Francois Mountains terrane lies within the Eastern Granite-Rhyolite province along the eastern margin of Laurentia and contains at least four mapped caldera complexes (Eminence, Lake Killarney, Butler Hill, and Taum Sauk), associated volcanic and volcaniclastic rocks, and four distinct types of intrusive units. The Mesoproterozoic rocks represent two major pulses of magmatic activity: (1) an older 1.48–1.45 Ga episode of caldera-forming volcanism and associated subvolcanic to massif-type granitic intrusions; and (2) a younger 1.33–1.28 Ga episode of bimodal intrusions. Volcanism included primarily high-silica rhyolite and volcaniclastic sediments associated with caldera-forming volcanism with lesser amounts of basalt and basaltic andesite that formed as flows and subvolcanic intrusions. The older (ca. 1.4 Ga) intrusive rocks can be divided into three broad categories: (1) granite massifs including the Butler Hill/Breadtray massif-type granites, (2) caldera ring–type granites such as the Silvermine Granite, and (4) mafic- to intermediate-composition intrusive rocks such as the Silver Mines Mafic Series. The younger (ca. 1.3 Ga) bimodal intrusions are represented by the highly evolved felsic Graniteville-types granites and the gabbros of the Skrainka Mafic Group. This field guide provides an overview of the magmatic history of the Mesoproterozoic rocks exposed in the eastern Saint Francois Mountains. Field-trip stops are divided into two days, highlighting well-known stops and lesser-known localities that illustrate the magmatic activity of one the premier igneous locations in the midcontinent region. The field trip is focused on two main areas. Day 1 focuses on the rhyolite sequence and associated caldera-forming eruption of the Taum Sauk caldera. Day 2 focuses on the volcanic rocks and granitic intrusions related to the Butler Hill caldera and ends with a visit to one of the youngest granitoids in the terrane, the Graniteville Granite. The field guide presents a summary of the volcanic history and petrogenesis of the Saint Francois Mountains rhyolites and granites.
5
Cahoon†, Emily B., Martin J. Streck†, and Mark Ferns†. "Flood basalts, rhyolites, and subsequent volcanism of the Columbia River magmatic province in eastern Oregon, USA." In From Terranes to Terrains: Geologic Field Guides on the Construction and Destruction of the Pacific Northwest, 301–52. Geological Society of America, 2021. http://dx.doi.org/10.1130/2021.0062(08).
Full textAbstract:
ABSTRACT The Miocene Columbia River Basalt Group (CRBG) is the youngest and smallest continental flood basalt province on Earth. This flood basalt province is a succession of compositionally diverse volcanic rocks that record the passage of the Yellowstone plume beneath eastern Oregon. The compositionally and texturally varied suite of volcanic rocks are considered part of the La Grande–Owyhee eruptive axis (LOEA), an ~300-km-long, north-northwest–trending, Middle Miocene to Pliocene volcanic belt that extends along the eastern margin of the Columbia River flood basalt province. Volcanic rocks erupted from and preserved within the LOEA form an important regional stratigraphic link between the flood basalt–dominated Columbia Plateau to the north, the north and bimodal basalt-rhyolite volcanic fields of the Snake River Plain to the east, the Owyhee Plateau to the south, and the High Lava Plains to the south and east; the latter two have time transgressive rhyolite centers that young to the east and west, respectively. This field-trip guide details a four-day geologic excursion that will explore the stratigraphic and geochemical relationships among mafic rocks of the CRBG and coeval and compositionally diverse silicic rocks associated with the early trace of the Yellowstone plume and High Lava Plains in eastern Oregon. The trip on Day 1 begins in Portland then traverses across the western axis of the Blue Mountains, highlighting exposures of the widespread, Middle Miocene Dinner Creek Welded Tuff and aspects of the Picture Gorge Basalt lava flows and northwest-striking feeder dikes situated in the central part of the CRBG province. Travel on Day 2 progresses eastward toward the eastern margin of the LOEA, examining a transition linking the Columbia River Basalt province with a northwestward-younging magmatic trend of silicic volcanism of the High Lava Plains in eastern Oregon. Initial field stops on Day 2 focus on the volcanic stratigraphy northeast of the town of Burns, which includes regionally extensive Middle to Late Miocene ash-flow tuffs and lava flows assigned to the Strawberry Volcanics. Subsequent stops on Day 2 examine key outcrops demonstrating the intercalated nature of Middle Miocene tholeiitic CRBG flood basalts, temporally coeval prominent ash-flow tuffs, and “Snake River–type” large-volume rhyolite lava flows cropping out along the Malheur River. The Day 3 field route navigates to southern parts of the LOEA, where CRBG rocks are associated in space and time with lesser known and more complex silicic volcanic stratigraphy forming Middle Miocene, large-volume, bimodal basalt-rhyolite vent complexes. Key stops will provide a broad overview of the structure and stratigraphy of the Middle Miocene Mahogany Mountain caldera and of the significance of intercalated sedimentary beds and Middle to Late Miocene calc-alkaline lava flows of the Owyhee basalt. Initial stops on Day 4 will highlight exposures of Middle to Late Miocene silicic ash-flow tuffs, rhyolite domes, and calc-alkaline lava flows overlying the CRBG across the northern and central parts of the LOEA. The later stops on Day 4 examine more silicic lava flows and breccias that are overlain by early CRBG-related rhyolite eruptions. The return route to Portland on Day 4 traverses the Columbia River gorge westward from Baker City. The return route between Baker and Portland on Day 4 follows the Columbia River gorge and passes prominent basalt outcrops of large volume tholeiitic flood lavas of the Grande Ronde, Wanapum, and Saddle Mountains Formations of the CRBG. These sequences of basaltic and basaltic andesite lavas are typical of the well-studied flood basalt dominated Columbia Plateau, and interbedded silicic and calc-alkaline lavas are conspicuously absent. Correlation between the far-traveled CRBG lavas and calcalkaline and silicic lavas considered during the excursion relies on geochemical fingerprinting and dating of the mafic flows and dating of sparse intercalated ashes.
6
Rhys, David A., Nadia St. Jean, Rodolfo Lagos, David Emmons, George A. Schroer, and Richard Friedman. "Chapter 18: Geology of Round Mountain, Nevada: A Giant Low-Sulfidation Epithermal Gold Deposit." In Geology of the World’s Major Gold Deposits and Provinces, 375–97. Society of Economic Geologists, 2020. http://dx.doi.org/10.5382/sp.23.18.
Full textAbstract:
Abstract The Round Mountain low-sulfidation epithermal Au deposit occurs within the rhyolitic tuff of Round Mountain (26.86 Ma) on the northeast side of an elliptical volcanic center that has morphology and volcanic facies suggesting it originated as a caldera. The hosting tuff comprises three pyroclastic flow and fall deposits (units T1 to T3). These are overlain successively by lacustrine sediments and volcaniclastic rocks. which may contain paleowater table levels formed at the time of ore formation and a 26.4 Ma postmineralization tuff unit. A linear vertical drop in the basement contact coincides with thick tuff fill and megabreccia, which is interpreted to follow the position of a WNW-trending ring fissure or vent wall that may have focused the locations of subsequent hydrothermal upflow zones. Orebodies are developed in strata-bound zones that are most extensive in poorly welded tuff, focused below overlying impermeable welded tuff in a WNW-trending, gently NW-plunging corridor above and mantling the SW-dipping paleoslope of basement rocks. Ore comprises disseminated pervasive adularia-quartz-pyrite ± illite alteration with electrum. The disseminated mineralization surrounds, and is most intensely developed in association with, a low-displacement extensional fault-vein network composed of conjugate NE- and SW-dipping faults and steeply dipping extensional veins. Vein orientations and kinematic indicators suggest ore formation occurred during localized NE-SW-directed extension that may have been related to late stages of volcanic subsidence, potentially in association with deep resurgent magmatism into ring fissures approximately 0.5 m.y. after deposition of the host tuff sequence.
7
Lane, Belden C. "Discernment: Taum Sauk Mountain and Jelaluddin Rumi." In Backpacking with the Saints. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780199927814.003.0023.
Full textAbstract:
Four hundred million years ago, Taum Sauk Mountain was a high ridge on a solitary island in a vast Paleozoic sea surrounded by coral reefs. Geologists describe it as a landscape of lofty volcanoes. It was one of the few parts of present-day North America that were never submerged under a primordial sea. At 1,772 feet above sea level, Taum Sauk Mountain has been worn down through the ages but is still the highest point in Missouri. It lies on the crest of a mountain chain several times older than the Appalachians. The Taum Sauk section of the Ozark Trail is one of the most beautiful stretches in the Ozarks. The twelve-and-a-half-mile tract that runs from the blue pools and massive boulders of Johnson’s Shut-Ins State Park to the top of Taum Sauk Mountain is studded with waterfalls, thick woodlands, rocky glades, and beaver ponds. It is a good place for reflecting on primeval things, gaining a long-range perspective on one’s life, discerning what has gone and what may yet need to come. This is one of the boons of wilderness hiking. Turning onto route CC off Highway 21 in Iron County on a Friday afternoon, I’ve made it to the top of the mountain a few hours before dark. My plan is to hike down the trail below Mina Sauk Falls, spending the night in the woods near Devil’s Tollgate and moving on toward Johnson’s Shut-ins the next day. I’ve come to an intriguing place. In wet weather, the water cascades 132 feet down rock ledges, forming the highest waterfall in the state. Below the falls the trail passes through an eight-foot-wide opening in a thirty-foot-deep section of magma that was part of an ancient volcanic caldera. Hardened now into fine-grained rhyolite, the geological oddity is dubbed the Devil’s Tollgate. A pioneer wagon road once passed between its stone walls, making a convenient site for bandits to hide. The locals claim that Jesse James hid out on the mountain after robbing the Ironton Train in 1874. Until the State Park System built a road to its top in the 1950s, Taum Sauk Mountain was a remote and isolated place.
Conference papers on the topic "Rhyolite calderas"
1
Moravec, Bryan G., Alissa White, Robert A. Root, Jennifer C. McIntosh, and Jon Chorover. "DECONVOLVING LEGACY AND CONTEMPORANEOUS WEATHERING IN A PORPHYRITIC RHYOLITE AND RHYOLITIC TUFF DOMINATED UPLAND CATCHMENT, VALLES CALDERA, NEW MEXICO." In GSA Annual Meeting in Indianapolis, Indiana, USA - 2018. Geological Society of America, 2018. http://dx.doi.org/10.1130/abs/2018am-324772.
Full text
2
Streck, Martin J., Elizabeth A. Brown, and Mark D. Schmitz. "AGES AND PETROGENESIS OF RHYOLITES AT TOWER MOUNTAIN CALDERA, EASTERN OREGON." In 68th Annual Rocky Mountain GSA Section Meeting. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016rm-276216.
Full text
3
Gardner, Jaime N., M. Magdalena Sandoval, Fraser Goff, Erin Phillips, and Ariel Dickens. "Geology of the Cerro del Medio moat rhyolite center, Valles Caldera, New Mexico." In 58th Annual Fall Field Conference. New Mexico Geological Society, 2007. http://dx.doi.org/10.56577/ffc-58.367.
Full text
4
Bryson, Alexis N., Stuart M. Kenderes, and Alan Whittington. "THROUGH A GLASS DARKLY; AN INVESTIGATION INTO THE VC-1 RHYOLITE, SW VALLES CALDERA, NM." In Joint 53rd Annual South-Central/53rd North-Central/71st Rocky Mtn GSA Section Meeting - 2019. Geological Society of America, 2019. http://dx.doi.org/10.1130/abs/2019sc-327380.
Full text
5
Phillips, Benjamin R., W. Scott Baldridge, Carl W. Gable, and James M. Sicilian. "Duration of the Banco Bonito rhyolite eruption, Valles Caldera, New Mexico, based on magma transport modeling." In 58th Annual Fall Field Conference. New Mexico Geological Society, 2007. http://dx.doi.org/10.56577/ffc-58.382.
Full text
6
Vazquez, Jorge A., Mark Stelten, and Kari M. Cooper. "FRACTIONATION, RECHARGE, AND REMELTING DURING THE EVOLUTION OF RHYOLITIC MAGMATISM AT YELLOWSTONE CALDERA." In GSA Annual Meeting in Seattle, Washington, USA - 2017. Geological Society of America, 2017. http://dx.doi.org/10.1130/abs/2017am-307244.
Full text
7
Joseph, William. "CHARACTERIZING CRYSTAL ASSEMBLAGES FOR THE PETROGENESIS OF POST-COLLAPSE RHYOLITES IN THE LONG VALLEY CALDERA, CALIFORNIA." In 112th Annual GSA Cordilleran Section Meeting. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016cd-274615.
Full text
8
Joseph, William T., and Terry L. Spell. "CHARACTERIZING CRYSTAL ASSEMBLAGES FOR THE PETROGENESIS OF POST-COLLAPSE RHYOLITES IN THE LONG VALLEY CALDERA, CA." In GSA Annual Meeting in Denver, Colorado, USA - 2016. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016am-280370.
Full text
9
Wolff, John A., J. N. Gardner, and S. L. Reneau. "Field characteristics of the El Cajete pumice deposit and associated southwestern moat rhyolites of the Valles Caldera." In 47th Annual Fall Field Conference. New Mexico Geological Society, 1996. http://dx.doi.org/10.56577/ffc-47.311.
Full text
10
Lente, Jenna L., and Emily R. Johnson. "VOLATILE CONTENTS AND PRE-ERUPTIVE CONDITIONS OF RHYOLITIC MAGMAS FROM THE ORGAN CALDERA, SOUTHERN NM." In GSA Annual Meeting in Denver, Colorado, USA - 2016. Geological Society of America, 2016. http://dx.doi.org/10.1130/abs/2016am-284230.
Full textReports on the topic "Rhyolite calderas"
1
Brown, Elizabeth. Rhyolite Petrogenesis at Tower Mountain Caldera, OR. Portland State University Library, January 2000. http://dx.doi.org/10.15760/etd.5881.
Full text
2
Phillips, Benjamin R., W. Scott Baldridge, Carl W. Gable, and James M. Sicilian. Duration of the Banco Bonito Rhyolite Eruption, Vales Caldera, New Mexico based on magma transport modeling. Office of Scientific and Technical Information (OSTI), March 2007. http://dx.doi.org/10.2172/1237263.
Full text
3
Self, S., M. L. Sykes, J. A. Wolff, and C. E. Skuba. Isotopic and trace element characteristics of rhyolites from the Valles Caldera, New Mexico. Final technical report. Office of Scientific and Technical Information (OSTI), September 1991. http://dx.doi.org/10.2172/10189843.
Full text
4
Marcy, Phillip. Revisiting Volcanology and Composition of Rhyolites and Associated REE Rich Mafic Clasts of the Three Fingers Caldera, SE Oregon. Portland State University Library, January 2000. http://dx.doi.org/10.15760/etd.1542.
Full text